This invention relates to faulted circuit indicators, and particularly to faulted circuit indicators having inrush restraints.
The use of faulted circuit indicators (or FCIs or fault indicators) to decrease the time of locating faults, either temporary or permanent in nature, on utility distribution systems is not new to the industry.
Since the early 1970's, when the use of FCI's began on a large scale, they have evolved from a "simple" high current trip and low current reset indicating device to an instrument that senses current wave shapes, recognizes presence and/or magnitude of voltage, uses real time to modify its trip and reset functions, beats the clearing time of low current rated current limiting fuses under high fault current conditions, disregards energization inrush currents, and a host of other features. When other options, such as various mounting configurations, types of indicating displays, polyphase sensing, etc. are included, there are will over 1000 types and styles available!
Attempts to disregard energization inrush currents have generally had limited success because they required an extended outage for operation and often were unable to ignore long term inrushes.